Water Exchange Research Articles

Water-medicated specifically targeting the S1 pockets among serine proteases using an arginine analogue

Because of the high similarity in structure and sequence, it is challenging to distinguish the S1 pocket among serine proteases, primarily due to the only variability at residue 190 (A190 and S190). Peptide or protein-based inhibitors typically target the negatively charged S1 pocket using lysine or arginine as the P1 residue, yet neither discriminates between the two S1 pocket variants. This study introduces two arginine analogues, L-4-guanidinophenylalanine (12) and L-3-(N-amidino-4-piperidyl)alanine (16), as novel P1 residues in peptide inhibitors. 16 notably enhances affinities across all tested proteases, whereas 12 specifically improved affinities towards proteases possessing S190 in the S1 pocket. By crystallography and molecular dynamics simulations, we discovered a novel mechanism involving a water exchange channel at the bottom of the S1 pocket, modulated by the variation of residue 190. Additionally, the specificity of 12 towards the S190-presenting S1 pocket is dependent on this water channel. This study not only introduces novel P1 residues to engineer inhibitory potency and specificity of peptide inhibitors targeting serine proteases, but also unveils a water-mediated molecular mechanism of targeting serine proteases.

RBFsim – A tool for early planning stage of riverbank filtration systems

Riverbank filtration (RBF) is increasingly being considered an effective method to support the management of water supply and the management of groundwater-river water exchange. Literature, however, provides very limited methods for the initial evaluation of the RBF system. Specifically, initial evaluations need to rely on limited data, be cost-effective, and provide sufficient useful output. The paper provides the development of a tool called RBFsim, designed for the early assessment of flow hydraulics in a riverbank filtration (RBF) scheme during site selection and optimization of well operation. The developed tool allows simplified computation (based on the Analytical Element Method or AEM) of the flow field for single and multiple wells in a 2D homogeneous and isotropic aquifer with uniform flow. The tool superimposes analytical solutions for key RBF quantities such as residence time (the time required for river water to reach the well) and the proportions of water (contributed by the river and groundwater) in the well discharge. These solutions are superimposed on the developed flow field. Additionally, the tool can be used to evaluate the impact of riverbed clogging on the operation of the RBF system. The simplified computation due to AEM and limited data requirements allows the tool to be used in handheld (smartphones) or desktop devices with or without internet connection. RBFsim results are verified by comparing them with results from MODFLOW and MODPATH simulations, which are based on entirely different (finite difference) computational schemes. The obtained results from both these models match within the error margin of less than 5%. Further, the practicality and applicability of RBFsim are illustrated using synthetic and field data. While the tool provides a matching river water contribution ratio with field data, it demonstrates the best-fit residence times primarily for higher well discharge rates. These limitations are attributed to complexities observed in the field, such as a heterogeneous aquifer and nonuniform flow. Overall, the developed tool simplifies the complex computations required, particularly for assessing the feasibility and risk of RBF schemes. The developed tool’s methods and code are open-sourced (licensed under CC-BY 4.0), which promotes personalized modifications and extensions.

КЫРГЫЗСТАНДЫН ТҮШТҮГҮНДӨГҮ АЙРЫМ СУУ САКТАГЫЧТАРДЫН ФИТОПЛАНКТОН БОЮНЧА ЭКОЛОГИЯЛЫК АБАЛЫ

The Papan and Naiman reservoirs are artificial reservoirs created to supply drinking water to the city of Osh and the settlements of the Nookat and Aravan regions. The object of study of ecology, including aquatic ecology (hydroecology, hydrobiology), is an aquatic ecosystem, which is an interconnected system of living organisms and their natural environment (water, sediments and adjacent land), in which substances and energy are formed, and there is a cyclic exchange of minerals and organic matter. Aquatic ecosystems are a complex type of artificially created reservoirs with a regulated water regime, as a result of which the level and speed of flow change, thereby determining the nature of the hydrobiological regime. The process of formation of a reservoir ecosystem depends on its specific conditions, initial biological resources, water exchange, anthropogenic loads, etc. Effective and environmentally safe use of water and biological resources of reservoirs can only be realized on the basis of a deep and comprehensive study of the structure and functioning of their ecosystems. The object of the study was the taxonomic composition of the phytoplankton of the Papan and Naiman reservoirs, located in the south of Kyrgyzstan. The relevance of the study is determined by the importance of these reservoirs in the national economy and in providing the population with clean water.

Modelling Mediterranean ocean biogeochemistry of the Last Glacial Maximum

Abstract. We present results of simulations performed with a physical–biogeochemical ocean model of the Mediterranean Sea for the Last Glacial Maximum (LGM) and analyse the differences in physical and biochemical states between the historical period and the LGM. Long-term simulations with an Earth system model based on ice sheet reconstructions provide the necessary atmospheric forcing data, oceanic boundary conditions at the entrance to the Mediterranean Sea, and river discharge to the entire basin. Our regional model accounts for changes in bathymetry due to ice sheet volume changes, reduction in atmospheric CO2 concentration, and an adjusted aeolian dust and iron deposition. The physical ocean state of the Mediterranean during the LGM shows a reduced baroclinic water exchange at the Strait of Gibraltar, a more sluggish zonal overturning circulation, and the relocation of intermediate and deep-water-formation areas – all in line with estimates from palaeo-sediment records or previous modelling efforts. Most striking features of the biogeochemical realm are a reduction in the net primary production, an accumulation of nutrients below the euphotic zone, and an increase in the organic matter deposition at the seafloor. This seeming contradiction of increased organic matter deposition and decreased net primary production challenges our view of possible changes in surface biological processes during the LGM. We attribute the origin of a reduced net primary production to the interplay of increased stability of the upper water column, changed zonal water transport at intermediate depths, and lower water temperatures, which slow down all biological processes during the LGM. Cold water temperatures also affect the remineralisation rates of organic material, which explains the simulated increase in the organic matter deposition, which is in good agreement with sediment proxy records. In addition, we discuss changes in an artificial tracer which captures the surface ocean temperature signal during organic matter production. A shifted seasonality of the biological production in the LGM leads to a difference in the recording of the climate signal by this artificial tracer of up to 1 K. This could be of relevance for the interpretation of proxy records like, e.g., alkenones. Our study not only provides the first consistent insights into the biogeochemistry of the glacial Mediterranean Sea but will also serve as the starting point for transient simulations of the last deglaciation.

Divergent response of energy exchange to heatwaves from flux tower observations among various vegetation types

Abstract The increasing frequency of European heatwaves and the associated impacts on ecosystems have raised widespread concern during the last two decades. The partitioning of surface energy between latent and sensible heat fluxes plays a pivotal role in regulating heat and water exchange between the land surface and the atmosphere. However, the responses of surface energy partitioning during heatwave events and the contributions of changes in energy partitioning to heatwave development have been underexplored. Here, we investigated the responses of surface energy exchange to temperature extremes during four devastating European heatwaves (2003, 2010, 2018, and 2022) based on long‒term observations from 31 flux towers. Our results demonstrated that the divergent responses of surface energy exchange to heatwaves were modulated by vegetation type and background climate in Europe. Forests maintained similar latent heat fluxes as the climatological mean but largely increased sensible heat under heat‒stressed conditions. While grasslands and croplands tended to increase sensible heat by suppressing latent heat during heatwaves, especially under water‒stressed conditions. Furthermore, the changes in surface energy partitioning strengthened positive land‒atmosphere feedbacks during the heatwave period, leading to unprecedented temperature extremes. This study highlights the importance of surface energy partitioning in land‒atmosphere interactions and heatwave developments.

Development of desalination plants within the semi-enclosed Persian Gulf

Although many desalination plants have been built in the countries around the Persian Gulf (PG) over the past decade, there exist crucial water demands in this region. Considering the limited water exchange between PG and the open seas, effluents more than the natural capacity of the PG will increase the sea-water salinity continuously. This excess salinity, in addition to threatening the marine ecosystems, endangers the water supply for many population centers. This study provides a comprehensive numerical analysis of the impact of existing and new desalination plants on the PG’s salinity. In addition, the water residence time and pollutant extension have been investigated in the PG. There exist several concerns, especially in recent years about the probable threat of desalination growth in semi-enclosed seas such as PG. The effect of desalination plants on the mean salinity of PG is one the questions investigated in this research. Results demonstrate that the water residence times in the southern and northwestern regions are more than five years. This time is reduced to nearly 26 to 45 months in the eastern regions near the Strait of Hormuz. Generally, the desalination plants have a negligible effect on the salinity of PG in comparison with the climate conditions such as evaporation and water exchanges. Based on the results, a 50% increase in effluent discharge of existing desalination plants increases the average salinity of the PG by only 0.01 psu. However, the annual volume of net evaporation (that exits the clean water directly) is nearly 36 times more than the effluent discharge from the existing desalination plants. Furthermore, this value is almost 0.2% of the amount of water that enters the PG through the Strait of Hormuz. In spite of these findings, the regional effects can be significant in some parts of the PG. For example, the southern and western coasts of PG are generally more vulnerable to pollution than other areas. The main reason is the shallow water depth in these areas and the water recirculation pattern. Some sensitive local areas have been also addressed in this study. Among the studied regions, the coastlines at the northwest of PG and at the north the Qeshm Island are two susceptible areas. The findings of this study underscore the importance of considering a new integrated viewpoint in developing desalination plants within PG.

Downscaling soil moisture in regions with high soil heterogeneity: the solution based on ensemble learning with sequential and parallel learner

Soil moisture plays an important role in the water and heat exchanges between the land surface and atmosphere, and it has great importance for agricultural production, ecological planning, and water resources management. Although microwave remote sensing has been widely used in large-scale soil moisture monitoring, the accuracy of the downscaled retrieval results cannot be guaranteed for regions with high vegetation coverage and high soil heterogeneity. To address these challenges, this study built soil moisture indice set based on MODIS and elevation data by calculating the Pearson correlation coefficient (R) and Maximum Information Coefficient (MIC), then constructed decision tree models (Gradient Boosting Decision Tree and Random Forest) about the indice set and low-resolution Soil Moisture Active Passive (SMAP) by using two ensemble learning methods (Bagging and Boosting). The models were applied to the high-resolution soil moisture indices in Jilin Province for the years 2017 to 2020 to generate 1 km-resolution products. In the validation process, Triple Collocation Analysis (TCA), comparison of soil moisture maps with coarse and fine resolution, and in-situ measurements in Lishu County, Tongyu County, and Jilin City were used to evaluate the differences between downscaling soil moisture results and ground observations at network, seasonal and point scales. The results were as follows: (1) The correlation coefficient (R2) calculated by the TCA method was 0.733 (GBDT_36km) > 0.649 (RF_36km), and the error variance was 0.0004 (GBDT_36km) < 0.00058 (RF_36km). (2) R at network scale was 0.798 (GBDT_SM) > 0.662 (RF_SM), RMSE was 0.040 (GBDT_SM) < 0.044 (RF_SM), the point scale R was 0.864 (GBDT_SM) > 0.833 (RF_SM), RMSE was 0.029 (GBDT_SM) < 0.039 (RF_SM). The R in four stages of the growth period was GBDT_SM > RF_SM, RMSE was GBDT_SM < RF_SM. In conclusion, the GBDT and RF models can reliably downscale soil moisture in Jilin Province, and the Boosting ensemble learning method represented by GBDT had a better estimation performance.

The Diffusion Exchange Ratio (DEXR): A minimal sampling of diffusion exchange spectroscopy to probe exchange, restriction, and time-dependence.

Water exchange is increasingly recognized as an important biological process that can affect the study of biological tissue using diffusion MR. Methods to measure exchange, however, remain immature as opposed to those used to characterize restriction, with no consensus on the optimal pulse sequence(s) or signal model(s). In general, the trend has been towards data-intensive fitting of highly parameterized models. We take the opposite approach and show that a judicious sub-sample of diffusion exchange spectroscopy (DEXSY) data can be used to robustly quantify exchange, as well as restriction, in a data-efficient manner. This sampling produces a ratio of two points per mixing time: (i) one point with equal diffusion weighting in both encoding periods, which gives maximal exchange contrast, and (ii) one point with the same total diffusion weighting in just the first encoding period, for normalization. We call this quotient the Diffusion EXchange Ratio (DEXR). Furthermore, we show that it can be used to probe time-dependent diffusion by estimating the velocity autocorrelation function (VACF) over intermediate to long times (~ 2-500 ms). We provide a comprehensive theoretical framework for the design of DEXR experiments in the case of static or constant gradients. Data from Monte Carlo simulations and experiments acquired in fixed and viable ex vivo neonatal mouse spinal cord using a permanent magnet system are presented to test and validate this approach. In viable spinal cord, we report the following apparent parameters from just 6 data points: , , , and , which correspond to the exchange time, restricted or non-Gaussian signal fraction, an effective spherical radius, and permeability, respectively. For the VACF, we report a long-time, power-law scaling with , which is approximately consistent with disordered domains in 3-D. Overall, the DEXR method is shown to be highly efficient, capable of providing valuable quantitative diffusion metrics using minimal MR data.

Water fluxes and energy partitioning over a Larix principis-rupprechtii plantation forest in a dryland mountain ecosystem, Northwest China

Plantations make up a sizable component of forest ecosystems in China's drylands and play an important role controlling the energy balance and water cycle. However, there is limited knowledge regarding the exchange of water and energy in dryland plantations, particularly those located within the intricate and unique environments of dryland mountain regions. The focus of this study was the investigation of a Larix principis−rupprechtii plantation within a dryland mountain ecosystem located in Northwest China. The eddy covariance method was employed to calculate the water and energy fluxes, while the thermal dissipation probe (TDP) method was utilized to measure forest overstory transpiration (T) from 2018 to 2021. The links between energy allocation and various components in water flux were investigated, as well as the variable dynamics of water and energy flux and their relationship with environmental conditions. The findings demonstrated that the annual mean cumulative evapotranspiration (ET) was about 510 mm, accounting for over 82.8 % of the precipitation, which was mainly from soil evaporation and understory transpiration, rather than overstory transpiration (T). The average value of T/ET was 0.25 for the growing season, and surface conductance (Gs) was always higher than canopy conductance (Gc) on both daily and monthly scales. The evaporative fraction (EF) and Priestley-Taylor model coefficient (α) in the growing season were significantly higher than those in the non-growing season, and α>1 from June to September, indicating that the ecosystem in the study area had sufficient water supply. Furthermore, during the growing season, the ratio of latent heat flux (LE) to net radiation (Rn) was larger than that in the non-growing season, while the proportion of sensible heat flux (H) was opposite, and soil heat flux (G) accounted for the smallest proportion of net radiation. This study provides valuable insights into the energy fluxes and water fluxes within the ecosystem of dryland mountain plantations, and it serves as a guide for choosing afforestation tree species in the future.

Drought effects in Mediterranean forests are not alleviated by diversity‐driven water source partitioning

Abstract Tree species diversity in forest ecosystems could reduce their vulnerability to extreme droughts through improved microclimate and below‐ground water source partitioning driven by contrasting species‐specific water use patterns. However, little is known about the seasonal dynamics of belowground water uptake that determine whether diversity positively or negatively impacts tree carbon assimilation and water exchange. Using a network of 30 permanent plots in Mediterranean forests with increasing tree species diversity (from monospecific to four‐species mixtures), we examined the seasonal patterns of in‐situ aboveground carbon and water relations and belowground water sources on 265 trees from four pine and oak species over 2 years using hydraulic and stable isotope approaches. We found that increasing species diversity in broadleaf and conifer mixtures induced strong soil water source partitioning between oak and pine species. As conditions became drier during the summer in mixed stands, oak species took up water from deeper soil sources, while pines were systematically limited to shallow ones. Despite significant belowground moisture partitioning, stronger drought‐induced reductions in photosynthesis, stomatal conductance, and leaf water potential were still observed in diverse compared with monospecific stands for pines but with some benefits for oaks. Synthesis: Our findings reveal that tree species diversity promoted belowground water source partitioning in mixed oak and pine stands, potentially reducing competition for water in more diverse ecosystems. Yet, our results show that it is insufficient to buffer the adverse impacts of severe droughts on aboveground tree carbon and water use, leading to higher water stress, especially for pines.

Simulation of Groundwater Dissolved Organic Carbon in Yufu River Basin during Artificial Recharge: Improving through the SWAT-MODFLOW-RT3D Reaction Module

To keep groundwater levels stable, Jinan’s government has implemented several water management measures. However, considerable volumes of dissolved organic carbon (DOC) can enter groundwater via water exchange, impacting groundwater stability. In this study, a SWAT-MODFLOW-RT3D model designed specifically for the Yufu River Basin is developed, and part of the code of the RT3D module is modified to simulate changes in DOC concentrations in groundwater under different artificial recharge scenarios. The ultimate objective is to offer valuable insights into the effective management of water resources in the designated study region. The modified SWAT-MODFLOW-RT3D model simulates the variations of DOC concentration in groundwater under three artificial recharge scenarios, which are (a) recharged by Yellow River water; (b) recharged by Yangtze River water; and (c) recharged by Yangtze River and Yellow River water. The study shows that the main source of groundwater DOC in the basin is exogenous water. The distribution of DOC concentration in groundwater in the basin shows obvious spatial variations due to the influence of infiltration of surface water. The area near the upstream riverbank is the earliest to be affected. With the prolongation of the artificial recharge period, the DOC concentration in groundwater gradually rises from upstream to downstream, and from both sides of the riverbank to the surrounding area. By 2030, the maximum level of DOC in the basin will exceed 6.20 mg/l. The Yellow River water recharge scenario provides more groundwater recharge and less DOC input than the other two scenarios. The findings of this study indicate that particularly when recharge water supplies are enhanced with organic carbon, DOC concentrations in groundwater may alter dramatically during artificial recharge. This coupled modeling analysis is critical for assessing the impact of recharge water on groundwater quality to guide subsequent recharge programs.

Integrating Hyperspectral Reflectance and Physiological Parameters to Detect Urban Tree Stress: A Study of Drought and Simulated Acid Rain

With urbanization and climate change worsening, urban trees are constantly exposed to environmental stress. To enhance the functionality and health of trees, it is crucial to rapidly and non-destructively detect and respond to tree stress. Research utilizing hyperspectral characteristics for detecting various stresses has recently been actively pursued. This study conducted comparative analysis using various leaf physiological parameters (chlorophyll content, chlorophyll fluorescence, leaf water, and gas exchange status) and hyperspectral data (VIS: visible ray; SWIR: short-wave infrared) to diagnose stress in Prunus yedoensis, commonly grown urban trees, by subjecting them simultaneously to different stresses (drought and simulated acid rain). The findings suggest that hyperspectral reflectance proved more responsive in identifying stress compared to the physiological parameters. Initially, VIS was more effective in detecting two stress responses than SWIR through a classification model (PLS-DA: partial least squares-discriminant analysis). Although SWIR initially faced challenges in simulated acid rain stress detection, spectral preprocessing (SNV: standard normal variate, + S.G 2nd: Savitzky–Golay 2nd derivative) enhanced its stress classification accuracy. Over time, the SWIR bands (1437 nm, 1667 nm, and 1949 nm) exhibited characteristics (such as moisture detection) more closely aligned with stress responses compared to VIS, as determined through PCA (principal component analysis). Hyperspectral reflectance also revealed the potential to measure chlorophyll fluorescence (Fo: minimum fluorescence). Building upon the foundational data of this study, the future potential of diagnosing urban tree stress using portable spectrometers is strong.

Effects of interfacial dynamics and nanoconfinement on the aggregation characteristics of CaSO4 in aqueous solutions inside 2D nanochannels

In this study, molecular dynamics simulations were used to investigate the effects of interfacial dynamics and nanoconfinement on the cluster characteristics and aggregation mechanisms of CaSO4 solutions inside two-dimensional (2D) nanochannels. Results reveal that CaSO4 clusters with low hydration are more likely to be found in 2D nanochannels than in a bulk solution. The interface region formed by layered water molecules results in the specific ion distributions inside a 2D nanochannel, affecting the hydration dynamics of Ca2+ ions near the interface region and ion-association characteristics. When Ca2+ ions migrate from the interface region to the bulk-like region, the association of Ca2+ and SO42− ions is promoted and the water exchange around CaSO4 clusters is enhanced, benefiting the formation of CaSO4 clusters with Ca2+ ions in high coordinated and low hydration degrees. Our results offer a microscopic understanding of the characteristics of prenucleation clusters and aggregation mechanisms in CaSO4 solutions inside 2D nanochannels, helping to control of the morphology and properties of CaSO4 precipitation.

Growth performance of African catfish (Clarias gariepinus) in aquaponic systems with varying densities of Vietnamese coriander (Persicaria odorata)

Mass cultivation of high-value aromatic herbs such as Vietnamese coriander and Persicaria odorata required specific soil, nutrients, and irrigation, mostly found in the limited natural wetland. This study aimed to evaluate the capacity of P. odorata at different densities in nutrient removal and the growth performance of African catfish, Clarias gariepinus in aquaponic systems. P. odorata was cultivated for 40 d with less than 10% water exchange. The effects of increasing crop densities, from zero plants for the control, 0.035 ± 0.003 kg/m2 in Treatment 1, 0.029 ± 0.002 kg/m2 in Treatment 2, and 0.021 ± 0.003 kg/m2 in Treatment 3, were tested on the growth performance of C. gariepinus with an initial density of 3.00 ± 0.50 kg/m3. The specific growth rate (SGR), daily growth rate of fish (DGRf), and survival rate (SR) of the C. gariepinus were monitored. Nutrient removal, daily growth rate of plant (DGRp), relative growth rate (RGR), and the sum of leaf number (Ʃn) of the P. odorata plant were also recorded. It was found that nutrient removal percentage significantly increased with the presence of P. odorata at different densities. The growth performance of C. gariepinus was also affected by P. odorata density in each treatment. However, no significant difference was observed in the DGRp and RGR of the P. odorata (p>0.05), except for Ʃn values. Treatment 1 had the highest Ʃn number compared to Treatment 2 and Treatment 3, showing a significant difference (p<0.05). This study demonstrates that the presence of P. odorata significantly contributes to lower nutrient concentrations, supporting the fundamental idea that plants improve water quality in aquaponic systems.

Impacts of Sea‐Level Rise on Coastal Groundwater Table Simulated by an Earth System Model With a Land‐Ocean Coupling Scheme

AbstractSea‐level rise (SLR) poses a severe threat to the coastal environment through seawater intrusion into freshwater aquifers. The rising groundwater table also exacerbates the risk of pluvial, fluvial, and groundwater flooding in coastal regions. However, current Earth system models (ESMs) commonly ignore the exchanges of water at the land‐ocean interface. To address this gap, we developed a novel land‐ocean hydrologic coupling scheme in a state‐of‐the‐science ESM, the Energy Exascale Earth System Model version 2 (E3SMv2). The new scheme includes the lateral exchange between seawater and groundwater and the vertical infiltration of seawater driven by the SLR‐induced inundation. Simulations were performed with the updated E3SMv2 for the global land‐ocean interface to assess the impacts of SLR on coastal groundwater under a high CO2 emission scenario. By the middle of this century, seawater infiltration on the inundated areas will be the dominant component in the land‐ocean coupling process, while the lateral subsurface flow exchange will be much smaller. The SLR‐induced seawater infiltration will raise the groundwater levels, enhance evapotranspiration, and increase runoff with distinct spatial patterns globally in the future. Although the coupling process is induced by SLR, we found topography and warming temperature have more control on the coupling impacts, probably due to the relatively modest magnitude of SLR during the selected future period. Overall, our study suggests significant groundwater and seawater exchange at the land‐ocean interface, which needs to be considered in ESMs.

Investigating nearshore spatial and temporal trends in nutrient concentrations along an urban northern shoreline, Lake Ontario

The nearshore zone of the Laurentian Great Lakes is of significant ecological importance, providing critical biogeochemical processes supporting spatially diverse habitats for a variety of species. Extreme plant and algal growth are common due to excessive anthropogenic eutrophication, with exacerbations from dreissenid establishment and lake mixing (e.g., coastal upwelling events and nearshore-offshore water exchanges), resulting in nuisance algal blooms across the nearshore area adjacent to Western Durham, Ontario, Canada. Thus, our main goal was to characterize the trends in essential nutrients (i.e., phosphorus and nitrogen) within the nearshore by applying general additive models on irregular time-series from 2011 to 2022 and to identify plausible contributing factors using exploratory principal component analysis. Increasing trends for total phosphorus were observed in surface (0.5 m below the surface) and benthic (0.5 m above the bottom) waters despite decreases in point source loading to the area. Most notably, the local water pollution control plant (WPCP) outfall did not seem to drive lake phosphorus concentrations across the study area, depicted by an orthogonal relationship within the principal component analysis. While the WPCP is a point source to the nearshore, it does not appear to be the primary driver of temporal lake phosphorus trends. Our results suggest that weather, inertial forcings and lake hydrodynamics in combination with traditional point-sources across Western Durham are contributing to the increasing total phosphorus trends observed as the peak period of wave spectra, wave height, alongshore wind speeds, watershed loadings, and total phosphorus concentrations within Lake Ontario were positively associated.

Study on recirculating aquaculture system (RAS) in organic fish production

Abstract The growth of conventional aquaculture has created environmental issues due to excessive feeding, low dissolved oxygen level etc into the water body. Organic aquaculture is a recent development as a solution to these issues. It is a clean alternative to reduce pollution and to produce safer consumable food. In the past few decades, recirculating aquaculture systems (RAS) were introduced to maintain pond water quality through lesser water exchange, by focusing on water reuse after treatment. In this study, the technical viability of RAS was analyzed for introduction in organic aquaculture systems. Indian major carps (IMCs) were cultured through conventional methods in the three tanks of conventional system, while the same species was grown organically in another three tanks in organic system. The stocking density and physical conditions were kept same for both cultured systems. The RAS consisted of fish culture tank with an average volume of each tank was 165 m3, a screen filter, foam fractionator and trickling filter. The various water quality parameters, i.e., solid size distribution in water, and removal efficiencies in biological treatment of both systems were compared. The present study, particle size distribution of solids in water body was measured by filtration, followed by weighing of dry residue solids. Pore sizes of 1000μ, 100μ, 20μ and 3μ were employed for filtration. For organic tanks, a majority of solids are of size between 1 mm and 100 μm. The larger sized particles (&gt; 30 μm) constitute nearly 70 % of the solids and the trait differs from the generalized conclusions of that a major part of sediments will be of sizes less than 20 μm. For the conventional tanks, majority of solids are of size between 3 mm and 20 μm and TAN shows higher removal efficiencies for effluents from organic system rather than conventional system. The results showed that organic aquaculture causes lesser pollution load per weight of fish. The particle size distribution of organic water was better compatible to screening and sedimentation than conventional water. Also the filtration efficiencies in nitrifying trickling filters of both water bodies were comparable, with that of organic water slightly on the higher side. Thus recirculating water treatment systems are introduced in organic aquaculture.

Spatiotemporal pattern of water age in Dongting Lake before and after the operation of the Three Gorges Project

Study regionDongting Lake Basin of China. Study focusDongting Lake is the first large-scale interconnected river–lake systems in the middle-lower reaches of the Yangtze River and the second-largest freshwater lake in China. Dam operation on the upper reaches of the Yangtze River dramatically affected the hydrological condition of Dongting Lake. Therefore, this study established a hydrodynamic-water age model to assess the effects of the Three Gorges Dam (TGD) on the spatiotemporal pattern of water age in Dongting Lake. New hydrological insightsThe results show a significant spatial and temporal variation of water age in Dongting Lake. Water age in the floodway is lower than that in the shoal, meanwhile, water age in spring and summer is lower than that in autumn and winter. By establishing a hydrodynamic-water age model, several factors influencing water age in Dongting Lake were analyzed, i.e., the influences of the Jingjiang Three Outlets' triage from the Yangtze River, the water level of the mainstream of the Yangtze River, and the flow pattern. The TGD could influence the water age in Dongting Lake by altering the hydrodynamic conditions of the Yangtze River. Results from this study provide support for flood control and dispatch management of Dongting Lake and provides a reference for water exchange studies in other large shallow lakes.

Temporal dynamics of microbial communities in the water of polyculture pond system for Chinese swimming crab Portunus trituberculatus

Microorganisms as the vital component of aquaculture ecosystems, were involved in nutrient cycling, water quality regulation, and the health of cultured species. In this study, aquatic water samples were collected monthly to reveal microbial community compositions, functions, and interactions in different habitats (pond and waterway) during the culture stages of the Chinese swimming crab Portunus trituberculatus in Shandong Province. Due to the semi-closed conditions with limited water exchange, the α diversities were lower in the polyculture pond. The relative abundances of the dominant phyla varied dramatically, and most biomarkers were identified in the polyculture pond. The β diversity of the microbial communities significantly differed among culture stages and habitats. Furthermore, the heterogeneity of prokaryotic microorganisms was greater than that of eukaryotic microorganisms. In the polyculture pond, the microbial community was sensitive to nutrient cycling, with abundant functions related to “photoautotrophy”, “nitrogen_respiration” and “nitrate_respiration”, corresponding to P. trituberculatus culture activities. The co-occurrence network of the microbial community in the polyculture pond tended to be looser than that in the waterway, with a lower number of taxa and correlations. In addition, these networks had nonrandom patterns and formed “small world” topological structures. The low-abundance genera with a higher level of betweenness centrality scores were the hubs or connectors in the networks and might play an essential role in microbial community composition. Furthermore, potential pathogens (Vibrio, Acholeplasma, Photobacterium, and Flavobacterium) deserve more attention during P. trituberculatus culture. This study will be useful for understanding microbial communities in polyculture pond systems and will provide a reference for the health aquaculture of P. trituberculatus.

Impact of engineering measures on water exchange and water quality in semi-closed bay: A model study in Zhelin Bay

Coastal aquatic environments are increasingly polluted due to human activities such as engineering, fishing, and agriculture. Semi-enclosed bays are particularly vulnerable to this issue due to weaker tidal currents and water circulation than open coastal areas. Although engineering measures, such as tidal channel dredging, have been implemented, their impact on semi-enclosed bays remains inadequately quantified. This study aimed to investigate the water exchange and water quality of Zhelin Bay, a semi-enclosed bay, after the implementation of two engineering measures: dredging the LG (Ligang) Channel and upgrading the SBM (Sanbaimen) Gate. The finite element model TELEMAC was used to simulate hydrodynamic processes before and after these two measures. The LG Channel dredging project increased flow velocity and tracer discharge during ebbing tides. The watergate project significantly reduced the semi-exchange time of adjacent waters. The combined two measures could enhance water exchange by up to 15 %. Furthermore, the projects slightly impacted spatial distribution of COD, while TP and TN levels near the SBM Gate decreased over by 80 %. This study represents the first effort to evaluate the water exchange improvement strategy of Zhelin Bay, a semi-enclosed bay with multiple tidal channels, and provides valuable insights for future research in marine ecology protection.